Turning to FIG. 1, an example of a conventional communication system 100 can be seen. This system 100 generally comprises a transmitter 102, a transmission medium 104, and a receiver 106. Typically, the transmission medium 104 is comprised of a pair of transmission lines that are configured to carry a differential signal from the transmitter 102 to the receiver 106. This type of system 100 is used in a wide variety of applications ranging from transmitting information over long distance (through cables) to on-chip communications. One issue with system 100 is that there is usually a length mismatch between the transmission lines in medium 104 that can lead to skew between the portions of the differential signal carried by the medium 104 (known as “intra-pair skew”), and an example of intra-pair skew can be seen in FIG. 2, where the transmission medium 104 for this example introduces 1 unit interval (UI) of skew. For low frequency signals, intra-pair skew can be largely ignored, but, for high frequency signals (i.e. >1 Gb/s), intra-pair skew can significantly impair communications.
To address intra-pair skew, several solutions have been proposed. These proposed solutions approach intra-pair skew as being a propagation delay issue, and an example of such a proposed solution can be seen in FIG. 3. As shown, skew compensator 200 (which is included within receiver 106) uses several delay elements 202-1 to 202-N coupled in series with one another to delay each portion of the differential signal accordingly to compensate for the intra- pair skew. Adjustments to the delay elements 202-1 to 202-N are made through adjustment of the control voltage VCNTL, but it can often be difficult to adequately adjust the relative delays to compensate for the intra-pair skew. Therefore, there is a need for an improved skew compensator.
Some other conventional circuits are: U.S. patent application Ser. No. 12/948,757; U.S. Pat. No. 6,335,647; U.S. Pat No. 6,909,980; U.S. Pat. No. 7,729,874; U.S. Patent Pre-Grant Publ. No. 2005/0099216; U.S. Patent Pre-Grant Publ. No. 2006/0244505; U.S. Patent Pre-Grant Publ. No. 2009/0174448.pdf; Zheng et al., “A 5 Gb/s Automatic Sub-Bit Between-Pair Skew Compensator for Parallel Data Communications in 0.13 μm CMOS,” 2010 Symposium on VLSI Circuits/Technical Digest of Technical Papers, Jun. 16-18, 2010; Olisar, Robert, “Unbalanced Twisted Pairs Can Give You the Jitters!,” Maxim Engineering Journal, Vol. 64, Sept. 2008, pp. 5-12.